AT THIS point, the policy legacy of George Bush seems pretty well defined by three disparate disasters: Iraq in foreign affairs, Katrina in social welfare, corporate influence over tax, budget and regulatory decisions. As a short-term political consequence, we may avoid another dim-witted Bush in the White House. But what the Bush dynasty has done to presidential campaign science — the protocols by which Americans elect presidents in the modern era — amounts to a political legacy that can haunt the Republic for years to come.

We are now enduring the third generation of Bushes who have taken the playbook of the "ruthless" Kennedys and amplified it into a consistent code of amorality in both campaign tactics and governance. In their campaigns, the Kennedys used money, image-manipulation, old-boy networks and, when necessary, personal attacks on worthy adversaries such as Adlai Stevenson and Hubert Humphrey. But there was also a solid foundation of knowledge and purpose undergirding John Kennedy's sophisticated internationalism, his Medicare initiative, his late-blooming devotion to racial justice, and Robert Kennedy's opposition to corporate and union gangsterism. Like Truman, Roosevelt and, yes, even Lincoln, two generations of Kennedys believed that a certain amount of political chicanery was tolerable in the service of altruism.

Behind George W, there are four generations of Bushes and Walkers devoted first to using political networks to pile up and protect personal fortunes and, latterly, to using absolutely any means to gain office, not because they want to do good, but because they are what passes in American for hereditary aristocrats. In sum, George Bush stands at the apex of a pyramid of privilege whose history and social significance that, given his animosity to scholarly thought, he almost certainly does not understand.

Here's the big picture, as drawn most effectively by the Republican political analyst Kevin Phillips in American Dynasty. Starting in 1850, the Bushes through alliance with the smarter Walker clan, built up a fortune based on classic robber-baron foundations: railways, steel, oil, investment banking, armaments and materiel in the world wars. They had ties to the richest families of the industrial age: Rockefeller, Harriman, Brookings. Yet they never adopted the charitable, public-service ethic that developed in those families.

Starting with Senator Prescott Bush's alliance with president Eisenhower and continuing through the dogged loyalty of his son, George H. W. Bush, to two more gifted politicians, presidents Nixon and Reagan, the family has developed a prime rule of advancement. In a campaign, any accommodation, no matter how unprincipled, any attack on an opponent, no matter how false, was to be embraced if it worked.

The paradigm in its purest form was seen when the first president Bush, in 1980, renounced a lifelong belief in abortion rights to run as Reagan's vice-president. To this day, any mention of this sell-out of principle sends the elder Bush into a rage. His son surpassed the father's dabbling with pork rinds and country music. He adopted the full agenda of redneck America — on abortion, gun control, Jesus — as a matter of convenience and, most frighteningly, as a matter of belief. Before the Bushes, American political slogans of the left and right embodied at least a grain of truth about how a presidential candidate would govern. The elder Bush's promise of a "kinder, gentler" America and the younger's "compassionate conservatism" brought us the political slogan as pure disinformation. They were asserting a claim of noblesse oblige totally foreign to their family history.

But whether Bush the father was pandering or Bush the son was praying, the underlying political trade-off was the same. The Bushes believe in letting the hoi polloi control the social and religious restrictions flowing from Washington, so long as Wall Street gets to say what happens to the nation's money. The Republican Party as a national institution has endorsed this trade-off. What we don't know yet is whether a GOP without a Bush at the top is seedy enough to keep it going. Dating back to the days when they talked of making George Washington a king, Americans have had an ambivalent attitude towards their aristocrats. They have also believed that dirty politics originated with populist Machiavellis such as Louisiana Governor Huey Long and urban bosses such as Chicago mayor Richard Daley. The Bushes, with their minders such as Rove, Cheney and DeLay, have turned that historic expectation upside down. Now political deviance trickles down relentlessly from the top. The next presidential election will be a national test of whether the taint of Bushian tactics outlasts what is probably the last Bush family member to occupy the executive mansion.

In 1988, the first president Bush secured office by falsely depicting his opponent as a coddler of rapists and murderers. In 2000, the present president Bush nailed down the nomination by accusing John McCain of opposing breast-cancer research. He won in 2004 with a barrage of lies about John Kerry's war record.

With the right leadership — the kind of flawed, but principled presidents sprinkled through its history — the United States can stop the blood-letting in Iraq, regain its standing in the world, avert the crises in health care and Social Security, and even bring disaster relief to the Gulf Coast.

But that's not simply a matter of keeping Bushes and Bushites, with their impaired civic consciences, out of the White House. The next presidential campaign will show us whether these miscreant patricians have poisoned the well of the presidential campaign system. If so, there's no telling what kind of president we might get.

Howell Raines is a Pulitzer Prize-winning former executive editor of The New York Times.